Changes in gene expression patterns are a hallmark of the aging process. Important insight into the mechanisms controlling such gene expression programs has come from the study of replicative senescence of cultured cells (eg, human diploid fibroblasts), which recapitulates many facets of cells from aging individuals. This Project has traditionally studied changes in RBP expression and function during replicative senescence. It has also examined the influence of RBPs in replicative senescence by interventions to elevate or reduce RBP levels, followed by the analysis of changes in senescence-associated mRNA expression patterns. We study if a given RBP binds a senescence-associated mRNA using a variety of in vitro binding assays (biotin pulldown, RNA EMSA, surface plasmon resonance/Biacore, etc) and assays to measure binding of endogenous molecules (ribonucleoprotein immunoprecipitation). To investigate RBP function during senescence, we employ approaches such as RBP silencing, RBP overexpression, and the identification of RBP-associated mRNAs using microarrays. We investigate whether RBPs affect the stability of target mRNAs during senescence, we measuring the steady-state levels and half-lives of the mRNAs of interest as a function of RBP abundance. We investigate whether RBPs affect the translation of target mRNAs by studying the relative assocation of the mRNA with translating polysomes and by quantifying the nascent translation rates of the encoded proteins. We also employ reporter constructs to gain additional insight into the processes modulated by RBPs and use various senescence-associated markers to examine changes in the senescence phenotype. During the past funding period, we have pursued several projects to study RBP expression in aging and age-related processes. In one of the projects, we discovered that the RBP HuR promotes the decay of the senescence-regulatory protein p16 (Chang et al., Mol. Cell. Biol. 2010) and in related work, we found that export of the HuR mRNA by HuR prevents the onset of replicative senescence ( Yi et al., Nuc. Ac. Res. 2010). In three separate pieces, we reviewed the RBPs and microRNAs that affect expression of diabetes- and obesity-related genes (Lee and Gorospe, Endocrinology, 2010), the RBPs and microRNAs described in 2009 with particularly close links to aging (Blagosklonny et al., Aging, 2010), and the implication of HuR in age-related diseases (Abdelmohsen and Gorospe, WIRES RNA, 2010).